Storage system

Abstract: The host adaptor package 4 and the disk adaptor package 6 which constitute the magnetic disk subsystem 1 are connected to the common bus 3 consisting of a data bus, a control bus, and a power line in the hot replacement ready state. The packages 4 and 6 have the control medium 11 and the clock generator 14 and when a failure occurs in a package, the replace controller 13 mounted in the control medium 11 executes the closing processing for the bus driver 15 and the clock generator 14. If this occurs, the clock generator 14 enters the closed state, so that the circuit in the package enters the reset state and the package function is stopped, that is, the package enters the closed state. As a result, hot replacement of the closed package can be executed without affecting the operation of the system.

Description: BACKGROUND OF THE INVENTION The present invention relates to a storage system which can be maintained unless power is turned off when an information processing unit is maintained and more particularly to a magnetic disk subsystem in which each package can be hotreplaced for the common bus. In a computer system which is used for plant control or a financial system at present, non-stop operation thereof is required. However, in a conventional computer system, when an error occurs in a part of the system, it is necessary to turn the power of system off once so as to execute a recovery operation. To run the system nonstop, it is necessary to replace or maintain the part where an error occurs without the power of system being turned off. There is an application regarding the hot replacement art for realizing such nonstop maintenance. In Japanese Patent Application Laid-Open No. Heisei 5-175678, an art that in an electronic device having a plurality of packages connected to a common bus, a controller installed outside the packages controls a bus buffer which is a connection circuit of the packages and common bus at the time of replacement of the packages and separates the packages logically from the common bus is indicated. Concretely, the art makes the impedance of the connection part of the bus buffer and common bus high. To run a computer system nonstop, it is effective to use an art for enhancing the reliability of the whole system, that is, to use a fault tolerance system which consists of a plurality of redundant systems. As this type of a prior art, a system consisting of a plurality of redundant systems in which the parts other than the interfaces of the redundant systems are operated by independent clocks for each redundant system is indicated in Japanese Patent Application Laid-Open No. Heisei 3-266011. SUMMARY OF THE INVENTION The electronic device indicated in Japanese Patent Application Laid-Open No. Heisei 5-175675 controls hot replacement and diagnosis of a plurality of packages intensively by a specific controller in the device. As a result, when a failure occurs in the controller, the system cannot be maintained nonstop. Only an art for separating the bus buffer logically from the common bus, that is, an art for separating the packages from a data system bus for transmitting data is indicated. Therefore, the effect on the whole system is not taken into account. In Japanese Patent Application Laid-Open No. Heisei 3-266011, a system which allows an operation by an independent clock for each redundant system is indicated. However, replacement of each redundant system during running of the system without affecting the operation of the system is not taken into account. In US-patent no. 4,870,643 a digital data storage system is disclosed with a plurality of Winchester disk drives, one drive serving as parity check storage unit, wherein a control circuit is provided so that any one of the disk drives may be unplugged and replaced without interruption of the storage system operation. US-patent no. 5,257,367 discloses a disk drive access control apparatus for connection between a host computer and a plurality of disk drives, one disk drive and its controller channel being provided to be used as a hot replacement in the event of a detected error. An object of the present invention is to provide a storage system consisting of a plurality of packages which share a bus and can be hot-replaced, wherein hot replacement of the packages can be executed without affecting the operation of the system. Another object of the present invention is to provide a magnetic disk subsystem, wherein each package is detachably mounted to the common bus and can be replaced without affecting the other packages. The storage system of the present invention has a plurality of logical devices connected to the host device constituting an interface to the host device, a storage device for storing data, a plurality of logical devices connected to the storage device constituting an interface to the aforementioned storage means, and a cache memory device for temporarily storing data transmitted between the aforementioned logical devices connected to the host device and the aforementioned logical devices connected to the storage device. These logical devices connected to the host device, logical devices connected to the storage device, and cache memory device consist of a plurality of packages which are connected to a common bus respectively which connects these devices to each other and each of the packages has a clock circuit for supplying a clock to the inner circuit and a control medium for executing the closing processing by stopping the supply of the clock to the inner circuit. Each package is connected to the common bus in the free replacement state. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a principle drawing of the present invention. Fig. 2 is a system configuration diagram of an embodiment of the present invention. Fig. 3 is drawings showing the configuration of the connectors and bus driver power controller and the operation timing for package replacement. Fig. 4 is a flow chart showing the procedure for replacing a package in which a failure occurs in the system operation state. Fig. 5 is a flow chart showing the procedure for replacing packages for maintenance in the system operation state. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail hereunder using an embodiment. Fig. 1 is a system block diagram of a storage system which will be explained in this embodiment. In this embodiment, a magnetic disk is used as a storage medium. However, other storage media may be used. A storage system using a magnetic disk as a storage medium, that is, a magnetic disk subsystem 1 consists of a common bus 3 and a host adaptor package 4, a cache package 5, a disk adaptor package 6, and a maintenance processor 9 (hereinafter referred to as an SVP 9) which are connected to the common bus 3. The common bus 3 consists of a data bus, a control bus, and a power line as shown in Fig. 2. The host adaptor package 4 is an interface with a host computer 2. The host adaptor package 4 has a data processing unit 10a for processing data, a bus driver 15 which is connected to the data processing unit 10a and is an interface to the host adaptor package 4 for the common bus 3, a control medium 11 for controlling data transmission thereof, and a clock generator 14 for generating an operation reference signal for each package. The control medium 11 has a package controller 12 for reporting the package operation status to the SVP 9 via a maintenance information bus 8 and a replace controller 13 for instructing the package closing processing in preparation for removal of a package by an instruction of the package controller 12 and for instructing initialization of a package after insertion. The package controller 12 has a microprocessor 16 (hereinafter referred to as an MP 16). The package controller 12 monitors the operation status of each package. When a failure occurs in a package, for example, an error occurs in data communication to the other package, the package controller 12 instructs closing of the package to the replace controller 13. When closing of the faulty package is instructed by the package controller 12, the replace controller 13 sends a PKOFF signal to the bus driver 15 and a reset signal to the clock generator 14 and the data processing unit 10a and executes the closing processing for the package 4. When the bus driver 15 receives the PKOFF signal, it enters the high impedance state for the common bus 3 and the package 4 is separated logically from the common bus 3. When at least the clock generator 14 enters the closed state, the circuit in the package enters the reset state and the package function is stopped, that is, the package enters the closed state. When the package enters the closed state, the power consumption of the package is reduced. By doing this, when the package 4 is removed, since the bus driver 15 is in the high impedance state for the common bus 3, it will not generate noise to the data bus and control bus of the common bus 3. Since the power consumption of the package is also reduced, the bus driver will not generate noise to the power line of the common bus. Therefore, in a magnetic disk subsystem to which the present invention is applied, a package can be removed in the state that the effect on other packages connected via the common bus 3 is reduced. The package controller 12 also detects a failure in the other package which responds via the common bus 3. The package controller 12 also can instruct closing processing for the other package in which a failure is detected. The cache package 5 which has not a package controller 12 consists of a data processing unit 10b, a control medium 11' having the replace controller 13, the clock generator 14, and the bus driver 15. The control medium 11' has not a package controller 12 unlike the control medium 11. Therefore, the closing processing for the package 5 is executed by the package controller 12 of the other package via the common bus. The disk adaptor package 6 has a configuration which is almost the same as that of the host adaptor package 4. However, a data processing unit 10c of the disk adaptor package 6 is connected to the bus driver 15 and a group of magnetic disks 7. The data processing unit 10c which is not shown in the drawing can be connected to a plurality of groups of magnetic disks 7. The group of magnetic disks 7 has a plurality of magnetic disk units 17. The magnetic disk units 17 are connected to the data processing unit 10c in parallel with each other. The disk adaptor package 6 has a package controller 12 in the same way as with the host adaptor package 4, so that it for itself can shift to the closed state. For a package which is newly inserted into the subsystem, a self diagnosis is executed by a package controller 12. This package is incorporated into the subsystem by an instruction of the SVP 9. A magnetic disk subsystem to which the present invention is applied maintains and replaces a package which operates normally, so that the magnetic disk subsystem instructs closing to the package controller 12 of a package to be maintained by operating the SVP 9. The SVP 9 is equipped with a display 18 and an input means which is not shown in the drawing. When a package to be maintained has not a package controller 12, the closing processing is executed for the package to be maintained via the package controller 12 of a package which is not to be maintained. As mentioned above, in a magnetic disk subsystem to which the present invention is applied, package failure monitoring and closing processing are executed for each package. Therefore, the system can realize its nonstop maintenance. A magnetic disk subsystem to which the present invention is applied has a clock generator 14 for each package. Therefore, the clock, that is, the intra-package reference frequency is supplied to each package. Accordingly, the clock signal supplied to each package will not be interrupted by closing of the other packages. As a result, the whole subsystem will not be stopped by a failure in a package. Furthermore, the other package which confirmed closing of the package informs the SVP 9 of closing of the package via the maintenance information bus 8. To instruct display of the closed package on the display 18 of the SVP 9, the SVP 9 can monitor an occurrence of a failure during package replacement and prevent incorrect package removal. Fig. 2 is a configuration diagram of a magnetic disk subsystem which is an embodiment of the present invention. Fig. 2 shows a more detailed constitution of the storage system shown in Fig. 1. In this embodiment, there are four host adaptor packages 4. Each host adaptor package controls data transmission between the host computer and a data bus 31. The host adaptor package 4 consists of a data transmission controller 41 having a data transmission control function for the data bus 31, a bus controller 52 for transmitting control information with a cache package 5 via a control bus 32, a clock generator 14 for supplying a clock to the inner circuit of the host adaptor package 4 via a supply bus which is not shown in the drawing, a microprocessor 16 (hereinafter called an MP 16) for receiving a data transmission request from the host computer and controlling (data transmission and failure monitoring) the host adaptor package 4, a LAN controller 44 for controlling communication with a maintenance LAN, a boot device 43 for storing the control program of the microprocessor which is a rewritable memory, for example, such as a flash ROM, a package close controller 45 for closing a package which is in preparation for removal of the host adaptor package 4 by an instruction of the MP 16, that is, for stopping the package function, a LED 46 for lighting so as to indicate that the host adaptor package 4 is in the closed state, a bus driver 47, a bus driver power controller 48 for controlling the power source of the bus driver 47 during replacement of the host adaptor package 4, and a main edge connector 60 corresponding to hot replacement for connecting the host adaptor package 4 and a main back plane 61. There are 8 disk adaptor packages 6 in the subsystem of this embodiment. Each disk adaptor package has a configuration which is almost the same as that of the host adaptor package 4. The disk adaptor package 6 is different from the host adaptor package 4 in that the data transmission controller 41 executes data transmission between the data bus 31 and the group of magnetic disks 7 and has a data transmission control function for the data bus 31 and the group of magnetic disks. However, the function of each of the bus controller 42, the clock generator 14, the MP 16, the LAN controller 44, the boot device 43, the package close controller 45, the LED 46, the bus driver 47, the bus driver power controller 48, and the main edge connector 60 of the disk adaptor package 6 is the same as that of the host adaptor package 4. The cache package 5 can be accessed commonly from the MP 16 of each adaptor. The cache package 5 consists of a shared memory 53 for storing various types of management information on the status and operation of each package, a shared memory controller 54 for transmitting information between the cache memory and each adaptor via the data bus 31, a cache memory 51 which exists between the host adaptor package 4 and the disk adaptor package 6 for temporarily storing data to be transmitted between them, a cache memory controller 52 for transmitting information between the cache memory and each package via the data bus 31, a package close controller 45 for closing a package in preparation for removal of a package by an instruction of the MP of the other package, a LED 46, a bus driver 47, a clock generator 14, and a bus driver power controller 48. When the contents of the shared memory 53 are lost, the subsystem cannot be operated. Therefore, to run the subsystem nonstop, it is necessary to duplicate the cache package 5 in preparation for replacement of the cache package 5. Therefore, the subsystem has two cache memories 5 for storing the same information. Fig. 3 is drawings showing the constitutions of the main edge connector 60 and the bus driver power controller 48 and the operation timing for package replacement. The pins of the main edge connector 60 are a general power pin 71 for supplying the package operation power, a signal pin 72 for connecting an output signal of the bus driver and the data bus or control bus, a bus driver bias signal pin 73 for giving a bias signal to the bus driver, and a ground pin 74. Hereafter, the data bus 31 and the control bus 32 to which the signal pin 72 is connected are referred to as a signal bus for explanation. The bus driver 47 has a characteristic that when a bias signal (Li) is given, the output signal thereof is biased and the capacitance of the output signal pin is reduced. When the power source (Vcc) is not connected, the output signal pin of the bus driver 47 is in the high impedance state. When a package is inserted, the pins of the main edge connector 16 are connected to the back plane in the order of (1) the ground pin 74 and the bus driver bias signal pin 73, (2) the signal pin 72, and (3) the general power pin 71. As a result, the output signal of the bus driver 47 when the signal pin 72 is connected is biased. Therefore, the potential of the signal pin 72 which is an output pin of the bus driver is close to the potential of the signal bus of the back plane. Furthermore, since the capacitance of the signal pin 72 is already low, an occurrence of noise due to leading-in of a current from the signal bus to the signal pin 72 can be suppressed. Since the general power pin 71 is connected last, when the signal pin 72 is connected, the signal pin 72 is in the high impedance state. Therefore, the signal pin 72 will not adversely affect the signal bus when it is connected. When a package is removed, the pins of the main edge connector 16 are disconnected in the order of (1) the general power pin 71, (2) the signal pin 72, and (3) the ground pin 74 and the bus driver bias signal pin 73. Before removing a package, the PKOFF signal is issued by the package close control circuit. As a result, the power supply to the bus driver 47 is interrupted and the output pin thereof enters the high impedance state. Therefore, when the signal pin 72 is separated from the signal bus, the signal pin 72 is in the high impedance state, and the potential thereof is close to the potential of the signal bus by the bias signal (Li), and the capacitance is low. As a result, the effect of noise on the signal bus by the signal pin 72 at the time of removal is suppressed. Fig. 4 is a flow chart showing the procedure when a package (host adaptor package 4, disk adaptor package 6) having an MP 16 in which a failure occurs is replaced in the system operation state. The package hot replacement processing procedure with an MP in the case of failure replacement will be explained hereunder with reference to Fig. 4. When a failure occurs in a package with an MP, the MP 16 in the faulty package detects the failure (Step 101). By an instruction of the MP 16 which detects the failure, the package close controller 45 issues a reset signal and a PKOFF signal to the inner circuit of the package (Step 102). Since the clock is halted by this reset signal, the operation of the inner circuit of the package is stopped and the power consumption of the package is reduced (Step 103). Since the bus driver power controller 48 which receives the PKOFF signal stops the power supply to the bus driver 47, the output of the bus driver 47 enters the high impedance state. Furthermore, the package close controller 45 turns the LED 46 on so as to inform a customer engineer of completion of closing of package. Now the preparation for package removal is completed (Step 104). On the other hand, a package which is operating normally confirms that the faulty package is closed via the control bus 32 (Step 105). The package informs the SVP of closing of the faulty package via the maintenance LAN 8 and writes the information of closed package into the shared memory 53 via the control bus 32 (Step 106). The SVP which is informed of closing of the package displays closing of the package on the display 21 (Step 107). The other packages can know closing of the package when they access the shared memory 53. The customer engineer confirms lighting of the LED 46 and display of the SVP 9 (Step 108) and then removes the closed package (Step 109). In this case, as mentioned above, the power consumption of the package to be removed is reduced by the package close controller 45. As a result, the power pin of the main edge connector 60 is prevented from damage due to an overcurrent when a package is removed. The output of the bus driver is also in the high impedance state. As a result, the effect of noise on the signal bus when a package is removed is suppressed and the operation of the whole system will not be affected. Next, the exchanged package is inserted by the customer engineer (Step 110). When the signal pin 72 of the main edge connector 60 is connected, the output signal of the bus driver 47 is biased. As a result, the potential of the signal pin 72 is close to the potential of the signal bus of the back plane. Furthermore, since the capacitance of the signal pin 72 is already low, an occurrence of noise in the signal pin 72 from the signal bus is suppressed. When the general power pin 71 is connected, the signal pin 72 is in the high impedance state. Therefore, the signal pin 72 will not affect the signal bus. When the package close controller 45 detects connection of the general power pin 71, a reset signal is issued to the exchanged package (Step 111) and the MP 16 of the exchanged package starts operation. The MP 16 of the exchanged package makes a self diagnosis (Step 112), operates according to the control program of the boot device 43, and diagnoses and initializes the exchanged package (Step 113). When an error is detected at the time of self-diagnosis at Steps 112 and 113, the package is closed and exchanged once again (Step 102). When the result of self-diagnosis shows no error, the exchanged package is incorporated into the subsystem by an instruction of the SVP 9 (Step 114) and starts the normal operation (Step 100). Fig. 5 is a flow chart showing the procedure when a package with an MP is replaced in the system operation state so as to maintain and replace it. The hot replacement processing procedure for a package with an MP in the case of maintenance and replacement will be explained hereunder with reference to Fig. 5. The SVP 9 issues a maintenance and replacement request by operation of the customer engineer (Step 200'). There are cases available that the maintenance and replacement request is issued to the MP 16 of a package to be maintained from the SVP 9 via the maintenance LAN 8 (Step 201) and the maintenance and replacement request is issued to the MP 16 of a package not to be maintained via the control bus 32 (Step 201'). In the former case, the MP 16 of the package to be maintained instructs the closing processing to the package close controller 45, and the closing processing is executed by the package close controller 45 (Steps 201 to 204), and the other package confirms closing of the package to be maintained (Step 205). In the latter case, the MP 16 of the package not to be maintained instructs the closing processing to the close controller 45 of the package to be maintained, and the closing processing is executed by the close controller 45 of the package to be maintained (Steps 201' to 204'), and the package not to be maintained confirms closing of the package to be maintained (Step 205). Next, hot replacement of the package is executed according to the same procedure (Steps 206 to 214) as that for replacement of a faulty package. A failure of a package (cache package 5) having no MP is detected by the MP 16 of a package with an MP via the control bus 32. The MP 16 of a package with an MP receives a maintenance and replacement request for a package with no MP and controls maintenance and replacement of the package with no MP via control bus 32 and data bus 31. The hot replacement processing for a package with no MP is executed according to the same procedure as that for a package with an MP. However, the closing processing for the package closing processing unit of a package with no MP which is to be removed or inserted is instructed by the MP 16 of a package with an MP via the control bus 32. According to this embodiment, in a magnetic disk subsystem consisting of a plurality of packages which can be hotreplaced for the common bus, an optional package can be hotreplaced without affecting the operation of the other packages in the system. According to this embodiment, by closing a package by the replace controller, the power consumption of the package is reduced and the effect on the power bus at the time of replacement is suppressed, so that the connector 60 is prevented from damage. According to this embodiment, the clock signal is supplied from each package, so that the whole subsystem will not be stopped due to a failure of a package, accordingly the failure resistance of the whole subsystem increases. In this embodiment, since a closed package can be confirmed easily, the whole subsystem will not be damaged due to misremoval. Since this embodiment has a plurality of confirmation means, a failure of a confirmation means mentioned above can be discovered easily. By still another operation of the present invention, an inserted package makes a self-diagnosis independently and is incorporated into the subsystem by an instruction of the SVP 9, so that the subsystem can operate regardless of insertion of the package and self-diagnosis thereof.As mentioned above, according to the present invention, in a storage system consisting of a plurality of packages which share a bus and can be hot-replaced, the packages can be hot-replaced without affecting the operation in the system.

Claims: A storage system, comprising: (a) at least one first package (4) connected to a host, for constituting an interface to said host; (b) at least one storage device (7) for storing data; (c) at least one second package (6) connected to said storage device, for constituting an interface to said storage device; (d) at least one cache memory package (5) for temporarily storing data transmitted between said first package connected to said host and said second package connected to said storage device; and (e) a common bus (3) for connecting said first packages, said second packages and said cache memory packages, to one another, each of said packages being detachably mounted to said common bus, wherein each of said first and second packages has a clock circuit (14) for supplying a clock to an inner circuit in each of said first and second packages, and a control medium (11), characterized in that each of said control media detects a failure which occurs in said package itself and executes a closing processing for said package by stopping supply of said clock to said inner circuit. A storage system according to claim 1, wherein each of said control media (11) detects a failure of the other package and executes the closing processing for said other package. A storage system according to claim 1, whereby said system has a maintenance medium (19) for monitoring the operation status of said package and maintaining a package in which a failure occurs. A storage system according to claim 3, wherein said maintenance medium (19) allows said control medium (11) to execute the closing processing.

Inventors: INOUE MITSURU, KUROSAWA HIROYUKI, INOUE, MITSURU, KUROSAWA, HIROYUKI
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1994
Main classification: G06F13
IPC codes: G06F13, G06F1, G06F3